11 Of the Latin authors, we worthily and justly call to mind St. Ambrose, who so earnestly inquired into all that was necessary in this cause, and so clearly ascribes what is due to each kind of man according to the laws of Christianity, that no one has ever achieved it better, whose sentiments, it is unnecessary to say, fully and perfectly coincide with those of St. Chrysostom.(20) These things were, as is evident, most justly and usefully laid down; but more, the chief point is that they have been observed wholly and religiously from the earliest times wherever the profession of the Christian faith has flourished. Unless this had been the case, that excellent defender of religion, Lactantius, could not have maintained it so confidently, as though a witness of it. "Should any one say: Are there not among you some poor, some rich, some slaves, some who are masters; is there no difference between different persons? I answer: There is none, nor is there any other cause why we call each other by the name of brother than that we consider ourselves to be equals; first, when we measure all human things, not by the body but by the spirit, although their corporal condition may be different from ours, yet in spirit they are not slaves to us, but we esteem and call them brethren, fellow workers in religion."(21)
Source: In Plurimis (Vatican.va)